1. Field of the Invention
The present invention relates to a hot pressing tool and hot pressing apparatus having the same, and more particularly, to an easily manufactured hot pressing tool which does not need an adjustment bolt due to reducing the thermal deformation, and a hot pressing apparatus having the same.
2. Description of the Related Art
A flat panel display which is small, lightweight, and has improved performance is in great demand, especially in the recently rapidly developing field of semiconductor technology. Among the flat panel displays with the qualities described above, liquid crystal displays (hereinafter, LCD) recently are in the spotlight and have advantages such as being small sized, lightweight, and having low power consumption. Thus, LCDs have been notably in the spotlight as an alternative means to overcome the disadvantages of conventional cathode ray tubes (hereinafter, CRT). Also, LCDs are currently provided and used for almost all information processing equipment needing display devices. Among the process of manufacturing LCDs as above, the assembly processing of connecting an LCD substrate and a tape carrier package (hereinafter, TCP) including a driving integrated circuit (IC) for driving the LCD is important for the reliability and the quality of LCDs.
Generally, a hot pressing and attaching method using an anisotropic conductive film (hereinafter, ACF) is used in the assembly process of connecting the LCD substrate and TCP. In this instance, since the TCP and LCD substrate are pressed together by hot pressing in a state where the tip of an attach equipment or the hot pressing head thereof is maintained at between 300 and 400° C., it is very hard to maintain the oblateness of the tip portion. In other words, the assembly process needs extremely precise thermal deformation control.
The above will be further described in detail with reference to FIGS. 1 and 2. FIG. 1 is a perspective view illustrating a conventional hot pressing tool, and FIG. 2 is a side view illustrating the conventional hot pressing tool. As illustrated in the figures, a conventional hot pressing tool 1 includes an adjustment block 10 moving up and down by a transfer instrument (not shown), a hot pressing head 40 making contact with the ACF of the LCD substrate and applying an electric current and performing the attachment, a head support 20 provided with the hot pressing head 40, and adjustment bolts 30 connecting the head support 20 and the adjustment block 10. The hot pressing head 40 is coupled with the head support 20 by combination bolts 26.
The head support 20 has heaters 25 embedded to heat the head support 20 and the hot pressing head 40. Generally, the head support 20 is formed using a beryllium copper alloy to enhance its thermal conductivity, and the hot pressing head 40 is formed using something different than the beryllium copper alloy that is used to form the head support 40 to enhance pressure strength.
The operation of the conventional hot pressing apparatus constructed as above will be described below.
An LCD substrate 60 is first provided on a support 50, and a transfer instrument later operates by control of a user to move the hot pressing head 40 down. At this time, the hot pressing head 40 is heated to a high temperature of more than 300° C. An ACF 62 is interposed between a TCP 61 and the LCD substrate 60 and the hot pressing head 40 presses the TCP 61 and the LCD substrate 60 for several seconds or dozens of seconds. In this manner, hot pressing is performed. After this, the hot pressing head 40 is moved up again by the transfer instrument. After removal of the vacuum state which provides adhesion, the LCD 60 substrate attached with the TCP 61 is taken out.
However, the conventional art as above has the following problems. Thermal deformation is a problem because the hot pressing head 40 of the hot pressing tool 1 presses the TCP 61 and the LCD substrate 60 at the state of a high temperature of more than 300° C. Thus, it is very hard to maintain the oblateness of the hot pressing head 40 because of the thermal deformation. Also, the compression precision of the TCP 61 and the LCD substrate 60 is not obtained because of the thermal deformation. This may cause a bad contact. The bad contact may result in the malfunction or error of an electric part. Consequently, the reliability of the product is deteriorated.
Also, the head support 20 and the hot pressing head 40 are formed using different materials. Thus, the oblateness is easily deteriorated because of their different thermal expansion coefficients. A thermal expansion coefficient of beryllium copper alloy is approximately below 17.5 μm/m° C. On the other hand, a thermal expansion coefficient of the hot pressing head 40 formed using a steel alloy is approximately between 10 and 12 μm/m° C. Accordingly, the oblateness error occurs because of the degree of different thermal deformation caused by different thermal expansion at the same temperature. The difference of thermal deformation coefficient between the beryllium copper alloy and the steel alloy is the underlying cause of a bad contact between the TCP, ACF and LCD.
Also, although the adjustment bolts 30 are provided to readjust the oblateness when thermal deformation occurs, it is very inconvenient to measure the oblateness and readjust the same through the adjustment bolts 30. Also, if the oblateness is measured and readjusted through the adjustment bolts 30 every process, it does not only decrease productivity, but also increases the cost of production because working hours get longer. Also, excessive adjustment may damage the adjustment bolt 30.